Its not a stupid question. But proof that the mind exists at all should be divided into two further questions: the existence of your own mind and the existence of other people minds.

You might, from listening to Descartes' comments about the unfeasibility of doubting your own thinking agency (eg consciousness), come to believe that whilst you can doubt your own body you cannot wholeheartedly doubt your own mind which David Chalmers would claim is a predicate for any experience.

If you have a painting, you could doubt what the painting is about but you cannot doubt the existence of the things that make it up; the oil based paints, the paper and suchforth. these it seems are necessary requirment for any prior illusion to occur.

The problem really then is with whether you can prove the existence of other people's minds. You could take the solopsistic approach and logically assume that you are the only mind in existence and that other people are mere robotic representations of mindful objects. But this doesnt seem to be intuitively correct; when you interact with someone in some way it seems too be that they are responding from their own mind and not from some complex circuitry.

John Stuart Mills suggests that because other people act in similar situations to you then they must have the same mental events and because you know that you have a mind, they must also possess one. For example, a person slipping on a banana may respond by cursing loudly. As this is a relevently similar action to the behaviour you would display given the same conditions, you can reasonably assume that the other person has a mind.

But is this really all that is required to say that other minds exist? That is the question I believe to be at the centre of the Mind Ontology debate.